Renewable Energy

By Izhar Ahmad DanishUpdated October 25, 2026Sources cited

Renewable energy is moving from a niche to the center of the power system. This guide explains what it is, how each source works, how much electricity it supplies today in the US and worldwide, where it struggles, and how you can use it at home. Every figure below names its source and data year.

What is renewable energy?

Renewable energy is energy from natural flows that refill on a human timescale: sunlight, wind, moving water, heat from inside the Earth and plant matter that regrows. Unlike coal, oil or natural gas, using it today does not shrink the amount available tomorrow.

The Intergovernmental Panel on Climate Change (IPCC) gives the standard scientific definition in its Special Report on Renewable Energy Sources (SRREN, 2011): renewable energy is any form of energy from solar, geophysical or biological sources that is replenished by natural processes at a rate that equals or exceeds its rate of use.

The idea rests on the difference between a flow and a stock. Fossil fuels are a stock: they formed over millions of years and every ton burned is gone. Sunlight and wind are flows: the sun delivers new energy every day whether we capture it or not. You can read more about that split in our guide to renewable resources and its counterpart, non-renewable resources.

Two related words get mixed up often:

• Renewable describes the source (it replenishes).
• Clean describes the emissions (little or no carbon dioxide or air pollution when generating). Most renewables are clean, and nuclear power is clean but not renewable, because uranium is mined from a finite stock. Our clean energy guide covers that distinction in detail, and sustainable energy adds the long-term tests of health, land and finite fuel.

In the US, renewables supplied about 9% of total energy consumption in 2023 (EIA) and about 24% of utility-scale electricity generation in 2025 (EIA). The electricity share is much higher because renewables mainly make power, while transport and industry still run largely on oil and gas.

History of renewable energy

Renewable energy is the oldest kind of energy people use, but the term “renewable energy” as a policy category dates from the 1970s oil crises. Before coal, households and workshops ran on wood, wind and water; the modern renewables era began when governments went looking for alternatives to imported oil.

For most of history, renewables were simply energy. Sailors used wind to move boats on the Nile as early as 5,000 BC, and by 200 BC wind-powered water pumps were in use in China and windmills were grinding grain in Persia and the Middle East (EIA, History of wind power). In the United States, wood was the main household fuel until the mid- to late 1800s and early industry ran on water mills, before coal and then oil took over (EIA, Today in Energy, 2013).

Electricity gave the old flows a new job. A water turbine drove a dynamo to light a theater and storefront in Grand Rapids, Michigan, in 1880 (US DOE, History of hydropower); Charles Brush ran a 12 kW wind turbine at his Cleveland mansion from 1888 (Mills Archive); and Bell Labs demonstrated the first practical silicon solar cell, about 6% efficient, on April 25, 1954 (IEEE Milestone).

The policy story starts with the 1973 oil embargo, when the price of a barrel first doubled and then quadrupled (US Office of the Historian). The US responded with the Public Utility Regulatory Policies Act (PURPA) of 1978, which for the first time forced utilities to buy power from independent small producers, including renewable plants (IEA policy database). In 1981 the United Nations held its Conference on New and Renewable Sources of Energy in Nairobi, which made “new and renewable sources of energy” part of the international vocabulary (UN Digital Library, A/CONF.100/11).

The 2009 founding of the International Renewable Energy Agency (IRENA) gave renewables their own intergovernmental body, and the 2015 Paris Agreement turned emissions cuts, and with them renewable build-out, into a near-universal national commitment.

How does renewable energy work?

Renewable energy works by converting a natural flow into a useful form, almost always electricity or heat. Most technologies spin a turbine connected to a generator; solar panels are the main exception, turning light directly into electricity.

The conversion paths fall into four groups:

1. Motion to electricity. Wind turbines, hydroelectric dams and tidal turbines use moving air or water to spin a rotor. The rotor turns a generator, where a magnet moving past copper coils induces an electric current.
2. Light to electricity. A photovoltaic (PV) cell is a thin layer of semiconductor, usually silicon, that releases electrons when photons hit it. Those electrons flow as direct current (DC), and an inverter converts it to the alternating current (AC) used by homes and the grid. See how solar panels work for the full process.
3. Heat to electricity or heating. Geothermal plants bring hot water or steam up from underground to drive a turbine. Concentrating solar power uses mirrors to heat a fluid that does the same.
4. Chemical energy to heat or power. Biomass such as wood, crop waste or biogas is burned or digested, releasing energy that plants captured from sunlight while growing.

Once generated, the electricity enters the same grid as power from any other plant. Your outlet cannot tell whether an electron came from a wind farm or a gas turbine; what changes is the fuel bill and the emissions behind it.

Output is measured in kilowatt-hours (kWh): one kilowatt of power delivered for one hour. If the unit is new to you, start with what is a kilowatt-hour.

What are the types of renewable energy?

There are six main renewable energy sources (solar, wind, hydropower, geothermal, biomass and ocean energy) plus green hydrogen, which is an energy carrier made with renewable electricity rather than a source in itself. Solar, wind and hydro produce most renewable electricity today.

A few notes on each:

• Solar is the fastest-growing source on the planet. It works anywhere the sun shines, from rooftops to desert power plants.
• Wind is the largest renewable source of US electricity. Onshore wind is cheap; offshore wind has stronger, steadier winds but costs more to build.
• Hydropower was the first large renewable source and is still the biggest worldwide. It can be dispatched on demand, which makes it valuable for balancing solar and wind.
• Geothermal runs around the clock. Power plants need hot rock near the surface, which in the US is concentrated in the West. A geothermal heat pump uses the steady temperature of shallow ground to heat and cool a building almost anywhere.
• Biomass is renewable only if the plants are regrown at the rate they are burned, and it still emits pollutants at the smokestack.
• Ocean energy is predictable (tides follow the moon) but the technology is early-stage and expensive.
• Green hydrogen is made by splitting water with renewable electricity in an electrolyzer. It stores and moves energy that was first generated by solar, wind or hydro, so it is a carrier, like a battery, not a primary source.

For a full list with examples, see our guide to renewable energy sources.

How much of our electricity comes from renewables?

Renewables produced about 24% of US utility-scale electricity in 2025 (EIA) and about 34% of global electricity in 2025, overtaking coal worldwide for the first time (Ember, Global Electricity Review 2026).

United States (EIA, 2025 data)

The US generated about 4.43 trillion kWh at utility-scale plants in 2025. The mix looked like this:

These figures exclude small rooftop solar systems, so the true solar share is somewhat higher.

World (Ember and IRENA)

• Renewables generated 34% of the world’s electricity in 2025, while coal fell to 33% (Ember, 2026).
• Solar reached 8.7% and wind 8.5% of global generation in 2025 (Ember, 2026). In 2024, hydropower was still the largest low-carbon source at 14.3% (Ember, 2025).
• Fossil fuels still supplied 57% of global electricity in 2025 (Ember, 2026).
• The world added a record 692 GW of renewable capacity in 2025, including about 511 GW of solar, bringing the total to about 5,149 GW (IRENA, Renewable Capacity Statistics 2026).
• Renewables made up 85.6% of all new power capacity added worldwide in 2025 (IRENA, 2026).

Which country is number one in renewable energy?

China is number one in renewable energy by volume: it generated about 3,920 TWh of renewable electricity in 2025, more than three times the United States, which ranked second at about 1,159 TWh. By share, Iceland, Paraguay, Ethiopia, Albania, Bhutan and Nepal get essentially all their electricity from renewables (Our World in Data, from Ember and the Energy Institute).

Volume and share tell different stories. Large economies lead on total output, while small countries with big rivers or volcanic heat lead on percentage:

Source: Our World in Data, share of electricity from renewables (Ember and Energy Institute data). The US figure includes small-scale solar, so it is slightly above the EIA utility-scale share of about 24%.

Note that “100% renewable” here means electricity only. No country runs its whole economy, including cars, planes and industrial heat, on renewables yet. Within the US, Texas generates the most wind power; Texas, Iowa, Oklahoma, Kansas and Illinois together produced about 52% of US wind electricity in 2025 (EIA).

Can the US run on 100% renewable energy?

Studies say a US grid with no fossil fuels is technically possible but would need a build-out far faster than today’s. A 2022 NREL study for the Department of Energy found several paths to 100% clean electricity by 2035, with wind and solar supplying 60–80% of generation and benefits exceeding costs (NREL/DOE, 2022).

That study counts nuclear and other zero-carbon plants as “clean”, so it is not a pure-renewables scenario. Its main requirements were:

• About 2 TW of wind and solar combined by 2035, many times the capacity installed in 2020.
• 120–350 GW of short-duration storage, mainly batteries.
• One to almost three times today’s transmission capacity, to move power between regions with different weather.
• Seasonal storage or firm clean power once clean sources pass about 80–95% of generation, to cover multi-day lulls in wind and sun.

Academic work goes further: Jacobson and Delucchi (2011) argued that all global energy could come from wind, water and solar using existing technologies (see scientific references below), but their findings remain debated. In practice, the US reached about 24% renewable electricity in 2025 (EIA), so the open questions are speed, transmission permitting and cost of firming, not physics.

What are the advantages of renewable energy?

The main advantages of renewable energy are near-zero emissions while generating, free fuel, low and falling costs, and energy security, because sunlight and wind cannot be embargoed or priced by a cartel.

• Low lifecycle emissions. Counting manufacturing, construction and disposal, NREL’s harmonized studies put wind at a median of about 11 g CO2e per kWh and solar PV below 50 g, compared with roughly 980 g for coal (NREL, Life Cycle Assessment Harmonization, 2012–2013 publications; see also Hsu et al., 2012 and Whitaker et al., 2012).
• Lowest cost for new power. Onshore wind’s global average levelized cost of electricity (LCOE) was $0.034/kWh and solar PV’s $0.043/kWh in 2024 (IRENA). LCOE is the average cost per kWh over a plant’s life, including building, financing and running it.
• Cheaper than new fossil plants in most cases. 91% of new utility-scale renewable capacity commissioned in 2024 produced power more cheaply than the cheapest new fossil fuel alternative (IRENA, 2025).
• No fuel price shocks. Once a wind or solar farm is built, its fuel costs nothing, which makes long-term power prices predictable.
• Cleaner air. Wind, solar, hydro and geothermal produce no smokestack pollutants such as sulfur dioxide or particulates while generating.
• Local and modular. A single home can install a few kilowatts of solar; a utility can install gigawatts. That flexibility lets households take part directly.

We go through all ten common benefits, with evidence for each, in advantages of renewable energy. Source-specific trade-offs are in solar energy pros and cons and wind energy pros and cons.

What is the biggest problem with renewable energy?

The biggest problem with renewable energy is intermittency: solar and wind produce power only when the sun shines and the wind blows, which is not always when people need it. Storage, grid upgrades, mineral supply and land use follow from that core issue.

1. Intermittency. Solar output drops to zero at night and falls in winter. Wind varies by hour and season. A grid running mostly on these sources needs backup, storage or flexible demand.
2. Storage. Lithium-ion batteries now shift solar power from afternoon into the evening peak, but they typically store energy for hours, not weeks. Covering a calm, cloudy winter week is still hard and expensive. Pumped hydro storage holds more, but needs suitable geography.
3. Grid and transmission. The best wind and sun are often far from cities. New high-voltage lines take years to permit and build, and many projects wait in long interconnection queues before they can connect.
4. Critical minerals. Clean technologies need more metal per megawatt. The IEA estimated that an onshore wind plant requires about nine times more mineral resources than a gas-fired plant of the same capacity, and a typical electric car about six times the minerals of a conventional car (IEA, The Role of Critical Minerals in Clean Energy Transitions, 2021). Mining and processing of lithium, cobalt, copper and rare earths is concentrated in a few countries.
5. Land use. Solar and wind farms spread over more land per unit of energy than a gas plant, although land under wind turbines can still be farmed and solar can go on rooftops, parking lots and degraded land.
6. Emissions still exist in some cases. Biomass releases carbon and pollutants when burned, and large dams can flood ecosystems and release methane from decaying vegetation.

None of these problems stopped renewables from passing coal in 2025 (Ember, 2026), but they explain why grid operators still keep gas and hydro plants on standby.

Renewable energy vs fossil fuels: how do they compare?

Renewable energy has lower emissions, free fuel and lower costs for new plants, while fossil fuels still win on round-the-clock availability and energy density. The table below sums up the trade-offs with sourced figures.

The cost ranges come from Lazard’s Levelized Cost of Energy+ (June 2025), which compares new US plants without subsidies. A deeper side-by-side, including nuclear, is in renewable vs nonrenewable energy.

How can you use renewable energy at home?

You can use renewable energy at home by installing rooftop solar panels, adding a battery, buying a green power plan from your utility, or switching to an electric heat pump and EV that can run on clean electricity. Start by measuring how many kWh you use, then size the system to match.

A practical sequence:

1. Measure your usage. Your utility bill lists monthly kWh. Our electricity usage calculator and kWh calculator break it down by appliance.
2. Price your current power. The US residential average was 18.2¢/kWh in August 2026 (EIA, Electric Power Monthly). Plug your own rate into the electricity cost calculator, and see how to lower your electric bill.
3. Size solar panels. The solar panel calculator estimates how many panels cover your usage, and the solar panel angle calculator finds the best tilt for your latitude. Our solar panel cost guide covers prices per watt and payback.
4. Plan storage or off-grid. For cabins, RVs or full independence, read our off-grid solar system guide and run the off-grid solar calculator and battery runtime calculator.
5. Consider wind or geothermal. A home wind turbine only makes sense on a windy, open lot; check it with the wind turbine calculator. A geothermal heat pump cuts heating and cooling energy almost anywhere.
6. Charge an EV on renewables. See the cost to charge an electric car and cost to charge a Tesla, or use the EV charging cost calculator.

One note on incentives: the federal Residential Clean Energy Credit (§25D) does not apply to systems placed in service after December 31, 2025, so budget for home solar without it and check state and utility programs instead.

Renewable energy facts

These renewable energy facts are drawn from EIA, Ember, IRENA, IEA and NREL data, each with its year.

• Renewables generated 34% of global electricity in 2025, overtaking coal (33%) for the first time (Ember, Global Electricity Review 2026).
• Solar supplied 8.7% of world electricity in 2025, almost matching nuclear at 8.9% (Ember, 2026).
• Clean power, renewables plus nuclear, reached 40.9% of global electricity in 2024 (Ember, 2025).
• Solar was the largest source of new electricity worldwide for the third year running in 2024, adding 474 TWh (Ember, 2025).
• The world installed a record 692 GW of renewable capacity in 2025, about three-quarters of it solar (IRENA, 2026).
• China, the US and the EU together accounted for 79.5% of new renewable capacity in 2025 (IRENA, 2026).
• Wind is the largest renewable source of US electricity at about 11% of utility-scale generation in 2025 (EIA).
• Renewables supplied about 9% of total US energy consumption, including transport and heating fuels, in 2023 (EIA).
• Onshore wind was the cheapest new source of electricity worldwide in 2024 at $0.034/kWh on average (IRENA, 2025).
• Wind power’s harmonized lifecycle emissions are about 11 g CO2e/kWh, roughly 1% of coal’s (NREL).

Scientific references

These peer-reviewed papers and assessment reports underpin the definitions, emissions figures and technology descriptions on this page.

• IPCC (2011). Renewable Energy Sources and Climate Change Mitigation: Special Report of the Intergovernmental Panel on Climate Change (O. Edenhofer et al., eds.). Cambridge University Press. doi:10.1017/CBO9781139151153
• Schlömer, S. et al. (2014). “Annex III: Technology-specific cost and performance parameters.” In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the IPCC. Cambridge University Press. doi:10.1017/CBO9781107415416 (PDF)
• Chapin, D. M., Fuller, C. S., & Pearson, G. L. (1954). “A New Silicon p-n Junction Photocell for Converting Solar Radiation into Electrical Power.” Journal of Applied Physics, 25(5), 676–677. doi:10.1063/1.1721711
• Hsu, D. D. et al. (2012). “Life Cycle Greenhouse Gas Emissions of Crystalline Silicon Photovoltaic Electricity Generation: Systematic Review and Harmonization.” Journal of Industrial Ecology, 16(S1), S122–S135. doi:10.1111/j.1530-9290.2011.00439.x
• Whitaker, M., Heath, G. A., O’Donoughue, P., & Vorum, M. (2012). “Life Cycle Greenhouse Gas Emissions of Coal-Fired Electricity Generation: Systematic Review and Harmonization.” Journal of Industrial Ecology, 16(S1), S53–S72. doi:10.1111/j.1530-9290.2012.00465.x
• Jacobson, M. Z., & Delucchi, M. A. (2011). “Providing all global energy with wind, water, and solar power, Part I: Technologies, energy resources, quantities and areas of infrastructure, and materials.” Energy Policy, 39(3), 1154–1169. doi:10.1016/j.enpol.2010.11.040
• Panwar, N. L., Kaushik, S. C., & Kothari, S. (2011). “Role of renewable energy sources in environmental protection: A review.” Renewable and Sustainable Energy Reviews, 15(3), 1513–1524. doi:10.1016/j.rser.2010.11.037

Bottom line

Renewable energy means power from flows that refill themselves: sun, wind, water, Earth’s heat and regrowing biomass. It already supplies about a quarter of US electricity (EIA, 2025) and a third of the world’s (Ember, 2026), and new solar and wind are usually the cheapest power you can build. The open problems are firming that variable supply with storage and transmission, and sourcing the minerals behind it.

For households the path is concrete: measure your kWh, then size solar, batteries or a heat pump with the free tools on this site. To keep reading, start with renewable energy sources or the full guides library.